Electromagnetism
Visão Geral
Every electric motor, every loudspeaker and every MRI scanner relies on the same principle: a current flowing through a magnetic field experiences a force. Electromagnetism connects electricity to magnetism and puts that connection to work in devices you use every day.
In this lesson you will trace the magnetic field around a current-carrying wire, build it into a solenoid, strengthen it into an electromagnet, and then apply Fleming's left-hand rule to predict forces. You will see how those forces drive a d.c. motor and make a loudspeaker cone vibrate to produce sound.
Objetivos
- Know that an electric current in a conductor produces a magnetic field around it
- Describe the construction of electromagnets
- Draw magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current
- Know that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field
- Understand why a force is exerted on a current-carrying wire in a magnetic field and how this effect is applied in simple d.c. electric motors and loudspeakers
- Use the left-hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
- Describe how the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current
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- What shape is the magnetic field around a straight current-carrying wire? A) Straight parallel lines B) Concentric circles C) Radial lines pointing outward D) A single loop Answer: B
- Which of the following will NOT increase the strength of an electromagnet? A) Increasing the current B) Adding more turns to the coil C) Using a copper core D) Using a soft iron core Answer: C
- In Fleming's left-hand rule, what does the thumb represent? A) Current B) Magnetic field C) Force D) Voltage Answer: C
- A wire carries a current of 6.0 A through a 0.50 T field. The wire is 0.20 m long. What is the force on the wire? A) 0.06 N B) 0.60 N C) 6.0 N D) 60 N Answer: B
- What is the role of the split-ring commutator in a d.c. motor? A) It increases the current B) It reverses the current direction every half-turn C) It strengthens the magnetic field D) It provides the power supply Answer: B
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